124 Remarks on Railway and Marine Signals. 



the proof supplied, that, under conditions very favourable to 

 rapid and complete desiccation, such as free exposure to air 

 and sun, bacteria may be destroyed in a comparatively short 

 time, not less, however, than from two to four days being 

 needed even in this climate in summer, and even longer, 

 unless the weather be actually hot. 



Since writing this paper I find from a passage in a letter 

 contained in Nature (vol. iil, p. 247), that Dr. Bastian had 

 been led to ascribe to the actinic rays of the sun an impor- 

 tant influence in promoting the spontaneous generation of 

 organisms in organic infusions. Though that notion may be 

 considered as fairly set aside by Professor Tynclall's experi- 

 ments, recorded in the Philosophical Transactions (part L, 

 1877), and again in his Essays on the Floating Matter of the 

 Air (p. 231), the interesting fact remains that, at different times, 

 both a favouring and an inimical action on the development 

 of these minute organisms should have been ascribed to the 

 sun's rays, when in reality they appear to have little, if any, 

 appreciable direct influence in either direction. 



Art. VIII. — Remarks on Railway and Marine Signals, 

 and on the Necessity of Accurate Testing of the Sight 

 of Signal and Look-out Men by Land and Sea. 



By James T. Rudall, F.RC.S. 



[Read 8th June, 1882.] 



The great increase of travelling in recent years, the large 

 numbers of ocean-going and other steamships, the frequency 

 of railway trains running over the same lines, and the 

 numerous intersections of these, have become attended by 

 dangers of which some cannot be wholly eliminated ; and 

 others, though avoidable, are only now beginning to receive 

 attention. 



If one remembers that between New York and Liverpool 

 nearly thirty large steamship companies have their vessels 



